In conventional power amplifier topologies linearity is often achieved by having large enough bias current in the transistor to ensure compliance to output requirements and specifications. This often results in the use of larger bias current than is required for supplying a certain output power to the load. This increases undesirable noise from the power amplifier. Another problem is that the transfer function from the input voltage to the output voltage is not linear due to the behavior of the transistor itself. This may provide undesirable signals. For example, the non-linear amplifier in a mobile telephone may produce signals in frequency bands that disturb other frequency bands. There is a need for a more effective and accurate power amplifier topology. Furthermore, the output impedance in conventional power amplifiers is dependant on the behavior of the output transistors which makes the output impedance inaccurate and constant only over a narrow frequency band.